x4c105 Intersil Corporation, x4c105 Datasheet - Page 5

• Manufacturer Part Number: x4c105
• Description: Cpu Supervisor With Novram And Output Ports
• Manufacturer: Intersil Corporation

SERIAL WRITE OPERATIONS
Byte Write
For a write operation, the device requires the slave
address byte and a word address byte. This gives the
master access to any one of the words in the array. After
receipt of the word address byte, the device responds
with an acknowledge, and awaits the next eight bits of
data. After receiving the 8 bits of the data byte, the device
again responds with an acknowledge. The master then
terminates the transfer by generating a stop condition, at
which time the device begins the internal write cycle to
the nonvolatile memory. During this internal write cycle,
the device inputs are disabled, so the device will not
respond to any requests from the master. The SDA out-
put is at high impedance. See Figure 5.
An attempted write to a protected block of memory will
suppress the acknowledge bit and the operation will
terminate.
Figure 5. Byte Write Sequence
Figure 6. Writing 12 bytes to a 16-byte page starting at location 10.
7 Bytes
Address
= 6
Signals from
Signals from
the Master
the Slave
5
SDA Bus
Address Pointer
Ends Here
Addr = 7
S
a
r
t
t
Address
Slave
0
X4C105
C
A
K
Address
Byte
Page Write
The device is capable of a page write operation. It is
initiated in the same manner as the byte write opera-
tion; but instead of terminating the write cycle after the
first data byte is transferred, the master can transmit
an unlimited number of 8-bit bytes. After the receipt of
each byte, the device will respond with an acknowl-
edge, and the address is internally incremented by
one. The page address remains constant. When the
counter reaches the end of the page, it “rolls over” and
goes back to ‘0’ on the same page. This means that
the master can write 16 bytes to the page starting at
any location on that page. If the master begins writing
at location 10, and loads 12 bytes, then the first 5
bytes are written to locations 10 through 15, and the
last 7 bytes are written to locations 0 through 6. After-
wards, the address counter would point to location 7 of
the page that was just written. See Figure 6. If the master
supplies more than 16 bytes of data, then new data
over-writes the previous data, one byte at a time.
Address
10
A
C
K
Data
5 Bytes
A
C
K
Address
S
o
p
t
n-1
March 18, 2005
FN8124.0